U.S. Pat. No. 5,248,856 for CODE-BASED, ELECTROMAGNETIC-FIELD-RESPONSIVE GRAPHIC DATA-ACQUISITION SYSTEM by Mallicoat, issued Sep. 28, 1993, describes a graphic data-acquisition system with respect to which the calibrator of the present invention is an improvement, and is incorporated in this disclosure for illustration purposes. Accordingly, the full disclosure of that patent is hereby incorporated by reference into this disclosure.
That patented data-acquisition system takes the form of a code-based, electromagnetic-field-responsive (and preferably optically responsive) system employing an active pair of transceivers, each including a rotating, multi-facet scanning mirror, and a laser whose beam is thereby scanned across a writing-surface area for the purpose of tracking the position, and noting certain characteristics respecting, different write-effective components, such as those just mentioned above.
For such a system to offer the highest degree of accuracy and reliability, it is important that the expanse, or expanses, of radiation created by the swept laser beams have a known, and preferably uniform, distance relation to the writing-surface area throughout the entirety of that area. This concern is not only present at the time that such a system is first assembled, but is also important later when the system is mounted for use, or in the event that something, over time, causes the writing-surface structure to warp, etc., in order to enable a user of the system to become aware that recalibration is necessary to return the system's capability to the normal and intended initial accuracy.
A key object of the present invention is to provide novel structure and a related method which promotes easy and ready calibration of a system of the type like that just described, as well as calibration monitoring over time to assess if and when a positional change occurs between the laser's scanning expanse and different portions of the writing surface.
Proposed, therefore, in accordance with the structure of this invention, are plural, distributed radiation-interactive units, or objects, which, herein, are preferably radiation-reflective units mounted adjacent what might be thought of as the four corners of the writing-surface area, and which interact with scanned radiation from the laser beams to effect the creation of related analog data streams that are interpretable by a processor in the system to assess the location of the expanse(s) relative to the writing surface. The term "radiation-interactive" is used herein to recognize that a relatively wide range of such things could be employed successfully, including occluders, absorbers, active interceptors, as well as reflectors, such as the ones that we specifically discuss hereinbelow. The reflecting units, chosen for use in the specifically disclosed system, also function to aid in system timing control with respect to successive scanning sweeps of the laser beams, all for the purpose of aiding in the tracking function mentioned above.
In the data-acquisition system which is specifically disclosed herein, that includes the calibration features of the present invention, there are also included three other improvements which are generally illustrated and/or mentioned herein, and which form the bases, respectively, of three different companion U.S. patent applications. These three companion applications include: "MARKING SYSTEM WITH PEN-UP/PEN-DOWN TRACKING", filed on Nov. 5, 1993 by Scott E. Wilson, Samuel W. Mallicoat and Donald H. Zurstadt now U.S. Pat. No. 5,454,270, "OPTICAL-SCANNING SYSTEM EMPLOYING LASER AND LASER SAFETY CONTROL", U.S. Ser. No. 08/148,691, filed on Nov. 5, 1993, by Guy L. Williams, Timothy A. Jenness and Scott E. Wilson; and "GRAPHIC DATA-ACQUISITION SYSTEM UTILIZING LIGHT-SOURCE STRUCTURE WITH EXTRANEOUS-LIGHT FILTERING", U.S. Ser. No. 08/148,600, filed on Nov. 5, 1993, by Timothy A. Jenness and Scott E. Wilson. The entire disclosures of these three companion applications are hereby incorporated herein by reference.
The various objects and features which are offered and obtained by the present invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.